Average is 175-225 people, with a mix of industry, government, and academia. Last year approximately half the papers submitted were from outside the US and we have growing mix of attendees from outside the US. It is a mixture of practitioners, researchers, engineers, etc. It is generally a very technical audience, and what separates us from some conferences is that there is a great deal of participation from the attendees....very little networking during the sessions (people gather before and after the sessions)...the hallways are empty during the tracks and tutorials.